It is known to stabilize a projectile in flight, thereby preventing tumbling, by ensuring that the centre of lift (also referred to as the center of pressure) is aft of the center of gravity of the projectile. The larger the static margin, which is the distance between the center of lift and the center of gravity as a proportion of the projectile length, the more stable the projectile is in flight. While a projectile may be stable at launch, events such as jettisoning of part of the projectile or of the body to which the projectile was previously attached during an earlier flight phase can cause the static margin to be altered such that it may no longer be sufficient to ensure stable flight.
It is also known to cause the centre of lift to move upon the occurrence of an event that changes the static margin, such as the aforementioned jettisoning of a body previously attached to the projectile.
For example, U.S. Pat. No. 6,871,818 and U.S. Pat. No. 6,869,043 each discloses a flare disposed toward the rear of the projectile, the flare having petals that deploy from a first, stowed position to a second, deployed position upon the occurrence of the event. In the stowed position, the petals are aligned with the air stream, in order to minimize drag. In the deployed position, the petals project into the air stream in such a way as to move the lift center rearward. A slide ring within the flare has sufficient inertia that it shifts aft in response to an acceleration that occurs when the attached body and the projectile are separated from one another. The slide ring is linked to the petals in such a way that the petals are deployed by the displacement of the slide ring. The slide ring is prevented from moving aft during launch of the projectile by slide supports which separate from the aft body when the separation event occurs. Detents lock the slide ring in its displaced position.
In U.S. Pat. No. 6,723,972, a method and apparatus are disclosed for planar actuation of a flared surface to control a vehicle. According to one aspect, there is disclosed an apparatus for controlling a vehicle capable of moving through a fluid medium. The apparatus includes a flare; a planar yoke operably associated with the flare; a plurality of actuators capable of moving the planar yoke to manipulate the flare through the operable association between the planar yoke and the flare; and a load bearing structure through which the translating means imparts a moment from the flare to the vehicle. According to another aspect, there is disclosed a method for controlling the maneuvering of a vehicle capable of moving through a fluid medium. The method includes moving a planar yoke to deflect at least a portion of a flare.